mptcp: send out ADD_ADDR with echo flag

When the ADD_ADDR suboption has been received, we need to send out the same
ADD_ADDR suboption with echo-flag=1, and no HMAC.

Suggested-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/options.c

@@ -242,7 +242,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		mp_opt->add_addr = 1;
 		mp_opt->port = 0;
 		mp_opt->addr_id = *ptr++;
-		pr_debug("ADD_ADDR: id=%d", mp_opt->addr_id);
+		pr_debug("ADD_ADDR: id=%d, echo=%d", mp_opt->addr_id, mp_opt->echo);
 		if (mp_opt->family == MPTCP_ADDR_IPVERSION_4) {
 			memcpy((u8 *)&mp_opt->addr.s_addr, (u8 *)ptr, 4);
 			ptr += 4;
@@ -579,10 +579,11 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	struct mptcp_addr_info saddr;
+	bool echo;
 	int len;
 
 	if (!mptcp_pm_should_add_signal(msk) ||
-	    !(mptcp_pm_add_addr_signal(msk, remaining, &saddr)))
+	    !(mptcp_pm_add_addr_signal(msk, remaining, &saddr, &echo)))
 		return false;
 
 	len = mptcp_add_addr_len(saddr.family);
@@ -594,22 +595,26 @@ static bool mptcp_established_options_add_addr(struct sock *sk,
 	if (saddr.family == AF_INET) {
 		opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 		opts->addr = saddr.addr;
-		opts->ahmac = add_addr_generate_hmac(msk->local_key,
-						     msk->remote_key,
-						     opts->addr_id,
-						     &opts->addr);
+		if (!echo) {
+			opts->ahmac = add_addr_generate_hmac(msk->local_key,
+							     msk->remote_key,
+							     opts->addr_id,
+							     &opts->addr);
+		}
 	}
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 	else if (saddr.family == AF_INET6) {
 		opts->suboptions |= OPTION_MPTCP_ADD_ADDR6;
 		opts->addr6 = saddr.addr6;
-		opts->ahmac = add_addr6_generate_hmac(msk->local_key,
-						      msk->remote_key,
-						      opts->addr_id,
-						      &opts->addr6);
+		if (!echo) {
+			opts->ahmac = add_addr6_generate_hmac(msk->local_key,
+							      msk->remote_key,
+							      opts->addr_id,
+							      &opts->addr6);
+		}
 	}
 #endif
-	pr_debug("addr_id=%d, ahmac=%llu", opts->addr_id, opts->ahmac);
+	pr_debug("addr_id=%d, ahmac=%llu, echo=%d", opts->addr_id, opts->ahmac, echo);
 
 	return true;
 }

net/mptcp/pm.c

@@ -13,11 +13,13 @@
 /* path manager command handlers */
 
 int mptcp_pm_announce_addr(struct mptcp_sock *msk,
-			   const struct mptcp_addr_info *addr)
+			   const struct mptcp_addr_info *addr,
+			   bool echo)
 {
 	pr_debug("msk=%p, local_id=%d", msk, addr->id);
 
 	msk->pm.local = *addr;
+	WRITE_ONCE(msk->pm.add_addr_echo, echo);
 	WRITE_ONCE(msk->pm.add_addr_signal, true);
 	return 0;
 }
@@ -135,15 +137,11 @@ void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
 	pr_debug("msk=%p remote_id=%d accept=%d", msk, addr->id,
 		 READ_ONCE(pm->accept_addr));
 
-	/* avoid acquiring the lock if there is no room for fouther addresses */
-	if (!READ_ONCE(pm->accept_addr))
-		return;
-
 	spin_lock_bh(&pm->lock);
 
-	/* be sure there is something to signal re-checking under PM lock */
-	if (READ_ONCE(pm->accept_addr) &&
-	    mptcp_pm_schedule_work(msk, MPTCP_PM_ADD_ADDR_RECEIVED))
+	if (!READ_ONCE(pm->accept_addr))
+		mptcp_pm_announce_addr(msk, addr, true);
+	else if (mptcp_pm_schedule_work(msk, MPTCP_PM_ADD_ADDR_RECEIVED))
 		pm->remote = *addr;
 
 	spin_unlock_bh(&pm->lock);
@@ -164,7 +162,7 @@ void mptcp_pm_rm_addr_received(struct mptcp_sock *msk, u8 rm_id)
 /* path manager helpers */
 
 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
-			      struct mptcp_addr_info *saddr)
+			      struct mptcp_addr_info *saddr, bool *echo)
 {
 	int ret = false;
 
@@ -178,6 +176,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 		goto out_unlock;
 
 	*saddr = msk->pm.local;
+	*echo = READ_ONCE(msk->pm.add_addr_echo);
 	WRITE_ONCE(msk->pm.add_addr_signal, false);
 	ret = true;
 
@@ -226,6 +225,7 @@ void mptcp_pm_data_init(struct mptcp_sock *msk)
 	WRITE_ONCE(msk->pm.rm_addr_signal, false);
 	WRITE_ONCE(msk->pm.accept_addr, false);
 	WRITE_ONCE(msk->pm.accept_subflow, false);
+	WRITE_ONCE(msk->pm.add_addr_echo, false);
 	msk->pm.status = 0;
 
 	spin_lock_init(&msk->pm.lock);

net/mptcp/pm_netlink.c

@@ -198,7 +198,7 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 
 		if (local) {
 			msk->pm.add_addr_signaled++;
-			mptcp_pm_announce_addr(msk, &local->addr);
+			mptcp_pm_announce_addr(msk, &local->addr, false);
 		} else {
 			/* pick failed, avoid fourther attempts later */
 			msk->pm.local_addr_used = msk->pm.add_addr_signal_max;
@@ -266,6 +266,8 @@ void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	spin_unlock_bh(&msk->pm.lock);
 	__mptcp_subflow_connect((struct sock *)msk, &local, &remote);
 	spin_lock_bh(&msk->pm.lock);
+
+	mptcp_pm_announce_addr(msk, &remote, true);
 }
 
 void mptcp_pm_nl_rm_addr_received(struct mptcp_sock *msk)

net/mptcp/protocol.h

@@ -169,6 +169,7 @@ struct mptcp_pm_data {
 	bool		work_pending;
 	bool		accept_addr;
 	bool		accept_subflow;
+	bool		add_addr_echo;
 	u8		add_addr_signaled;
 	u8		add_addr_accepted;
 	u8		local_addr_used;
@@ -442,7 +443,8 @@ void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
 void mptcp_pm_rm_addr_received(struct mptcp_sock *msk, u8 rm_id);
 
 int mptcp_pm_announce_addr(struct mptcp_sock *msk,
-			   const struct mptcp_addr_info *addr);
+			   const struct mptcp_addr_info *addr,
+			   bool echo);
 int mptcp_pm_remove_addr(struct mptcp_sock *msk, u8 local_id);
 int mptcp_pm_remove_subflow(struct mptcp_sock *msk, u8 remote_id);
 
@@ -464,7 +466,7 @@ static inline unsigned int mptcp_add_addr_len(int family)
 }
 
 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
-			      struct mptcp_addr_info *saddr);
+			      struct mptcp_addr_info *saddr, bool *echo);
 bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 			     u8 *rm_id);
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);